The t(l; 19) translocation in pediatric ALL identifies a subgroup of patients with poor prognosis who might benefit from more aggressive chemotherapy. This reciprocal translocation results in the expression of a novel fusion protein with oncogenic properties which is not expressed in normal tissues. Antibodies to this fusion protein can serve as a valuable adjunct to classical cytogenetics for more accurate diagnosis and prognosis, eventually leading to development of individualized treatment modalities and earlier detection of recurrent disease. Using molecular techniques to produce recombinant fusion protein as immunogen, monoclonal antibodies will be generated and screened for their utility in various immunological assays including flow cytometry, immunocytology, immunoblotting, and immunoprecipitation. The availability of MAbs against E2A/pbxl fusion protein, the gene product of t(l;19) translocation, would eventually be used clinically for improved diagnosis and subclassification of ALL. PROPOSED COMMERCIAL APPLICATION: The MABs generated during the Phase I grant would allow us to develop immunodiagnostic test kits for pediatric t(l;19) pre-B ALL through the envisioned Phase II grant. Such kits would facilitate the identification of high-risk patients who might benefit from intensified chemotherapeutic regimens, and for detection of minimal residual disease and early relapse. Since ALL is the most common malignancy in children and 5-6% of all pediatric ALL's carry the t(l; 19) translocation, it has potential worldwide market.